Well should avoid carrying heavy load despite the need to do groceries shopping. When you carry heavy load, you are using extra force and strain your abdominal area esp. Sometimes you feel the pain womb/abdominal area due uterus stretching or baby's growing. As long as baby's moving, doing healthy it is fine.
It could be ligament pain or uterus stretching. Need to also consider how long the pain lasts, the severity, and if it's associated with bleeding. Observe it and if you're bothered then best to check with your doctor ☺️